However I use a Check Point VPN client behind a NAT router and this (the VPN client) has a specific option to:

Use NAT transversal tunneling:

and

IKE over TCP
or
Force UDP encapsulation.

I use the IKE over TCP setting. My router (a Vigor 2600) has no specific forwarded ports and my connection "just works"...

Working fine now - "plug n play"

After spending hours testing, contacting Pipex (never easy) to confirm protocol support, reconfiguring my router etc, IT at work advised that they had issued me with an incorrect password and username.

Assh-les!

Thanks for your help anyway.....

.. IT departments hey...!